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Sender: Richard Henderson <rth7680@gmail.com>
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Date: Fri, 16 Aug 2013 12:46:03 -0700
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Subject: Re: [Qemu-devel] [PATCH v2] exec: Fix non-power-of-2 sized accesses
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To: Alex Williamson <alex.williamson@redhat.com>
Cc: lersek@redhat.com, qemu-devel@nongnu.org, qemu-stable@nongnu.org

On 08/16/2013 08:37 AM, Alex Williamson wrote:
> On Fri, 2013-08-16 at 08:27 -0700, Richard Henderson wrote:
>> On 08/16/2013 05:50 AM, Alex Williamson wrote:
>>> +    /* Size must be a power of 2 */
>>> +    if (l & (l - 1)) {
>>> +        while (l & (access_size_max - 1)) {
>>> +            access_size_max >>= 1;
>>> +        }
>>> +    }
>>> +
>>
>> Why the loop at all?  x & -x extracts the lsb of x.
> 
> l = 5, we want 4, not 1.  Thanks,

It still doesn't require a loop.

  l = 1 << (31 - clz32(l));


r~